Clamps are widely used in aircraft as well as numerous other applications for attaching a tube/conduit to a support member. Normally the support and tube/conduit are constructed of metal.
Some of these clamps are referred to as “P-clamps” because they have the cross-sectional shape of a clamp that is shaped like the letter “P.” An example of a conventional P-clamp is shown in FIG. 1. As can be seen in the figure, the clamp 100 includes a looping body 102 which is used to secure the tube. Body 102 is clamped about the tube (not shown) when an upper flange 104 is brought together with a lower flange 106. The flanges 104 and 106 are integral with the metal spine 108 of the loop portion 102. The metal spine 104 is included in a flexible protective covering 110. The covering is provided so that the metal will not damage the tubing. Although the covering 110 protects the tube from mechanical damage, it also acts as an insulator. Thus, electrical charges developed or induced in the tubing are not discharged, which can create sparks creating a fire hazard.
Conventional systems for dealing with charge buildup within aircraft fuel tank systems has typically involved either bulky and complicated bond strap arrangements or expensive conductive couplings. Bond strap installations create maintenance difficulties when tubing must be inspected or replaced, and have failure modes which create potential ignition sources when exposed to the effects of lightning. In particular, improper installation or vibration and fretting of bond straps can result in frayed elements that can act as ignition sources under certain conditions.
U.S. Patent Application Publication No. 2012/0225571 made by Shapiro is not a P-clamp, but instead, uses two fasteners to secure a padded metal piece to a structure in order to secure a tube. Shapiro discloses a metal comb structure which acts as a static drain.